On Christmas Eve 2012, in Tower Sky, a 120-story skyscraper in the center of Seoul, South Korea, different individuals are living their lives according to their own paths: the strong-willed manager of a Chinese restaurant, Yoon Hee (played by Son Ye-jin), the reserved building property manager and single father Lee Tae-ho (played by Kim Sang-gyung), a domineering and rude socialite, the president who looks down on others, and a careless little chef who often forgets things... They go about their daily routines, sometimes crossing paths, sometimes unrelated to each other, unaware that a disaster is about to strike them. As night falls and people immerse themselves in the romantic and happy atmosphere created by artificial snow, an unexpected accident occurs. A helicopter, designed for snowmaking, loses control due to strong air currents and crashes into the building, triggering chaos and an uncontrollable inferno. The once heavenly and luxurious skyscraper instantly transforms into a brutal hell on earth...